On Sat, 2007-12-01 at 14:56 -0500, Dave Robillard wrote: > No argument that it's faster. With separate int fractional parts it's > even probably cleaner. I may be convinced... > > Taking a step back, it would be nice to have these events (being > generic) able to use something other than frame timestamps, for future > dispatching/scheduled type event systems. OSC uses 64 big fixed point > absolute time stamps, giving a resolution of about 200 picoseconds > absolute time (epoch January 1, 1900). This is equivalent to NTP time > stamps apparently - ie huge precedent. > > Whether stamps are in frames or absolute time could be a property of the > port. Maybe we should up it to 64 bits fixed point? The additional 32 > bits aside, doing that gives us all the range or precision in frames > needed, and the ability to map to a widespread absolute timestamp > format, and parity with OSC. That's a lot of pros... > > (This may sound a bit esoteric, but to do something like Max right, you > need absolute time stamps). > > Currently in MIDI we have 64 bits in there anyway.. I never thought of > using fixed point, but the OSC/NTP parity and potential for very precise > absolute time stamps is very, very tasty to me. > > Also, the frame part would be a uint32_t - equivalent to Jack MIDI > timestamps, another win (and cutting out more conversion overhead).
Another thought on 32:32 fixed point with a 'timestamp type' concept: tempo time. You could use these stamps at beats:ticks time stamps with excellent range/resolution. Actually now that I think of it I've run into exactly this problem in Ardour MIDI with floating point tempo-time-stamps. 32:32 stamps like this would be excellent in a sequencer, I would definitely use them in Ardour. With the same event struct we can get: - Sub-sample accurate frame timestamps (Jack MIDI stamps + resolution) - Absolute timestamps with sub-nanosecond resolution (OSC equivalent) - Tempo relative timestamps with much higher resolution than any existing MIDI/sequencer/etc gear I know of ++ -DR- _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
